Subshell Differential Photoionization Studies of Single- and Multi-Walled Fullerene Endohedrals

单壁和多壁富勒烯内面体的亚壳层差分光电离研究

• 批准号: 0758224
• 负责人: HIMADRI CHAKRABORTY
• 金额: $ 12万
• 依托单位: Northwest Missouri State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0758224&HistoricalAwards=false
• 关键词: Subshell; Differential; Photoionization; Studies; Single

The encapsulation of atoms in fullerenes offers a unique natural laboratory to examine the behavior of an atom in confinement. Studies of these endohedral compounds can not only lead to intriguing effects at the atomic scale but also can probe subtleties of quantum effects in the nanometer region. Besides the single-wall confinement, the multi-walled confining shell of nested concentric single-walled fullerenes, bucky-onions,can make the coupling of the central atom with the shell rich in novel effects.Technologically also the endohedral fullerenes hold the promise of exciting applications:(a) Research is underway to use endohedrally doped fullerenes and bucky onions as seed materials in solid state quantum computations, in which quantum bits can be encoded in the electronic and nuclear spins of the encapsulated atoms. (b) Recent experiments with Ar@C60 find evidence of encaged atoms significantly improving the superconducting ability of materials. (c) A proposed biomedical application of endohedral materials is to shield radioactive tracers inside fullerene cages, and then inject the material into human blood to monitor blood flow. (d) The ability of fullerenes to sequester metal atoms inside has led to exploring their potential as contrast-enhancing agents for magnetic resonance imaging. The discovery of endo fullerenes with trapped noble gases in extraterrestrial environments indicates the astrophysical relevance of their studies. Therefore, understanding the influence of the confining cage on thespectroscopy of the atom inside, and vice versa, are matters of significant interest.A theoretical photoionization study of these compounds is proposed. Photoionization is a well known method to obtain a fairly undistorted account of the many-electron dynamics of the discrete and continuum states of atomic systems, since the coupling of the photon with the electrons is so weak and the photon disappears in the final channel.Employing this tool we will investigate the role of the collective motion of delocalized electrons in endohedrally doped single- and multi-walled fullerenes. Cross sections and asymmetry parameters of the ionization from both atomic and fullerene sub-shells will be calculated to understand the many-body interactions that determine the photoabsorption properties of these nanoparticles.Moreover, the diffraction of atomic photo-liberated electrons in crossing the confining wall will be studied in detail in the spirit of a recently discussed Fourier photo-spectroscopy approach.

原子在富勒烯中的封装提供了一个独特的天然实验室来研究原子在限制中的行为。对这些内嵌化合物的研究不仅可以在原子尺度上产生有趣的效应，而且可以在纳米区域探索量子效应的微妙之处。除了单壁约束外，嵌套同心单壁富勒烯的多壁约束壳也可以使中心原子与壳的耦合具有丰富的新效应。在技术上，内嵌富勒烯也有令人兴奋的应用前景：(a)研究正在进行中，使用内嵌掺杂的富勒烯和洋葱作为固态量子计算的种子材料，其中量子比特可以在封装原子的电子和核自旋中编码。(b)最近通过Ar@C60进行的实验发现，包裹原子显著提高了材料的超导能力。(c)内嵌材料在生物医学上的一种建议应用是将放射性示踪剂屏蔽在富勒烯笼内，然后将该材料注入人体血液中监测血流。(d)富勒烯将金属原子隔离在里面的能力使人们开始探索其作为磁共振成像对比度增强剂的潜力。外太空环境中含有惰性气体的内富勒烯的发现表明了他们的研究与天体物理学的相关性。因此，了解封闭笼对内部原子光谱的影响，以及反之亦然，是非常有趣的事情。提出了这些化合物的理论光电离研究。由于光子与电子的耦合非常弱，光子在最终通道中消失，因此光电离是一种众所周知的方法，可以获得原子系统离散和连续状态的多电子动力学的相当完整的描述。利用这个工具，我们将研究局域电子在内腔掺杂的单壁和多壁富勒烯中的集体运动的作用。将计算原子和富勒烯亚壳电离的截面和不对称参数，以了解决定这些纳米粒子光吸收特性的多体相互作用。此外，原子光释放电子在穿过围壁时的衍射将以最近讨论的傅里叶光谱学方法的精神进行详细研究。